In commercial applications for food heating it is necessary to provide relatively large heating compartments for containing food intended for cooking, baking, frying, thawing, etc. It is desirable that heat in such heating compartments be relatively uniformly distributed throughout the same for uniform or controlled heating of product therein. It is desirable, too, that the entire appliance, i.e. a gas convection oven, be capable of being cleaned with relative ease in order to maintain high standards of cleanliness. It also is important to maintain a high degree of reliability of the equipment and facility of servicing the same.
In U.S. Pat. No. 3,605,717 there is disclosed a convection oven in which combustion of gas effects the primary heat input. Disclosure of such patent is incorporated in its entirety by reference. In such patent there is disclosed principles of convection heating in a commercial heating appliance.
Food placed inside a convection oven is processed by moving heated air along a circulatory path directed and arranged to provide throughout the food chamber or heating chamber substantially uniform temperatures of a preselected and controllable level. The circulatory path is generally defined by the walls of the oven, by baffling and by the food supporting means in the food chamber. The air is moved along the circulatory path by a fan or blower usually located adjacent the food chamber in a convection blower chamber. The blower is in the circulatory path.
In the past, the circulated air and gases in convection ovens has been heated by passing them over and around electrically heated coils, steam pipes, heated flues, or tube-like heat exchangers, such as that shown in the noted patent, and relying only upon an exchange of heat between the heating system and the air the desired air temperature in the oven could be maintained. In the noted patent, too, is disclosed the possibility of allowing the products of combustion actually to enter the circulatory air path of the convection oven but this occurs at a limited outlet area of the convection blower air flow. In such patent the burner is of the type that directs a jet of gas into the heat exchanger tube. The inlet to the heat exchanger tube, however, also is open to the atmosphere so that air may be drawn into the heat exchanger tube to support combustion of the gas. The amount of air entering the heat exchanger tube, thus, is uncontrolled, and there is the possibility of unwanted material entering the open inlet of the heat exchanger tube.
The heat exchanger tube disclosed in such patent has several linear lengths connected together at angles to extend generally parallel to several of the walls of the convection blower chamber so that air blown by the convection blower would flow across at least several of those linear tubular extents to be heated by the hot gases flowing through the latter. A conical inlet baffle guides air from the heating or food chamber toward the center or inlet of the convection blower wheel, and a perimeter portion of such baffle and the oven walls guide air flow from the outlet of the convection blower wheel, as such air flows past the heat exchanger, into the heating compartment. Baffles on walls of the heating compartment and the oven walls further guide air flow toward the food or the material therein.